1. Field of the Invention
The present invention relates to programmable electronic signs, and particularly to such signs wherein segmented character displays are controlled by character selection cards or memory-stored data that specify which display segments are to be illuminated.
2. Description of the Prior Art
Electronic signs in which several different messages are displayed sequentially have gained widespread acceptance because they are so effective in attracting the attention of prospective customers. Typically such signs have one or more rows of individual character displays each of which can exhibit any letter of the alphabet, any numeral, or certain symbols such as a hyphen, percent sign, etc. By appropriate wiring or programming means, the sign can be made to display any word, message or sequence of messages.
A principal shortcoming of prior art electronic signs is their complexity and hence high cost. One object of the present invention is to provide a low cost electronic sign which though simple in design nevertheless permits user selection and modification of each displayed message, and which can sequentially display a plurality of such messages.
The individual character displays used in electronic signs typically comprise a matrix of lamps that are selectively illuminated to produce the desired character. Recently other alphanumeric display configurations have come into vogue, such as the 16-segment display having sixteen separate rectilinear and diagonal segments.
In most prior art signs, character information specifying the desired messages was stored in an alphanumeric code format such as the ASCII code. Complex decoding was required to convert this alphanumeric code into drive signals to energized the requisite display segments that produce the corresponding character. A memory capable of storing such multi-bit alphanumeric codes was required. Entry of new messages necessitated coding into this format. Thus, in certain systems it was necessary to prepare a punched tape containing the new message, and to use a tape reader to enter this data into the memory. In contrast, it is another object of the present invention to provide an electronic sign in which message data is stored and handled directly in the form of segment illumination data bits. That is, instead of storing the ASCII or other conventional alphanumeric code, each character is stored as a set of bits each of which specifies whether a corresponding display segment is to be energized. Data storage, decoding and display drive requirements thereby are substantially simplified.
A further object of the present invention is to provide an inexpensive means for entering a new message. Keyboard and encoding systems, or punched tape assemblies of the prior art, are costly. Although they provide considerable speed and possibly simplify altering the message content, they are not acceptable for low cost displays. In contrast, the present invention uses a set of printed circuit programming cards associated with respective alphanumeric characters. The message is chosen by inserting appropriate ones of these cards having the desired message characters. By coding these cards directly with segment illumination data, system simplicity and low cost is achieved.